I have no idea what the difference is. If the RSE are aligned with the Typhon Pact, and we know that the Pact's agenda seems to be in contrast with the Federation/Klingon Alliance and their new allies that have joined the Khitomer Accords (the IRS included), then the treaties shold be in question.
Didnt the book only say that certain interstellar powers had been invited to a summit to discuss the expansion of the Khitomer Accords to include them? And if I remeber correctly, the book said that among them only the Ferengi had even formally agreed to attend at that point. (Donatra's Romulans may have agreed too, but I would have to go find the book and check up for that).
Personally I would be surprised to see, beyond maybe the IRS, any of them actually join the accords and Alliance.